1992 Toyota Land CruiserFACTORY OEM SERVICE PROCEDURE

Idle Speed Control (ISC) System

  1. Listen for clicking sound at ISC valve immediately after engine is shut off. The ISC valve is located on air intake chamber, near throttle body.
  2. If no sound is heard, check ISC valve and wiring circuit between Electronic Control Unit (ECU) and ISC valve. See appropriate wiring diagram in WIRING DIAGRAMS article in the ENGINE PERFORMANCE Section. The ECU is located near the glove box.
  3. To check ISC valve resistance, ensure ignition is off. Disconnect electrical connector from ISC valve. Note ISC valve terminals. See Fig 1.
  4. Using ohmmeter, measure resistance between specified terminals. See ISC VALVE RESISTANCE SPECIFICATIONS table. Replace ISC valve if resistance is not within specification.
    ISC VALVE RESISTANCE SPECIFICATIONS

    Terminals Ohms
    B1 To S1 Or S3 10-30
    B2 To S2 Or S4 10-30
    NOTE: Before removing ISC valve, drain coolant from cooling system. Remove both coolant by-pass hoses.
  5. To check ISC valve operation, remove ISC valve. Apply battery voltage to terminals B1 and B2. See Fig 2-Fig 3 . Repeatedly ground terminals in sequence and ensure ISC valve closes and opens. See ISC VALVE GROUNDING SEQUENCE table. Replace ISC valve if defective.
ISC VALVE GROUNDING SEQUENCE

Application Terminal Grounding Sequence
To Close ISC Valve S1-S2-S3-S4
To Open ISC Valve S4-S3-S2-S1
Fig 1: Identifying ISC Valve Terminals
G92J27671Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
Factory Service Tools

Use the Manual With the Right Hardware

Pair factory procedures with proven DIY tools so the instructions are easier to execute.

Disclosure: Verified tool recommendations may earn an affiliate commission at no cost to you.

Shop Manual-Ready ToolsCompare Repair QuoteQuote Shield Pro

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.

Rather have a pro handle this?

A certified mobile mechanic comes to your home or office. They bring the tools, you stay comfortable. No tow truck, no waiting room, no surprises.

Comes to youSame-day available12-month warranty
Get a Free Quote

No obligation. See pricing before you book.